News media hype of sunscreen studies leaves readers burned by speculative evidence

 Carolina Branson, PhD, is an associate editor with She tweets as @BransonCarolina.

Man showing sunburn line by liftng t-shirt sleeve.Just in time for beach season, the news media are serving up a confusing hodgepodge of stories, one claiming that sunscreen can reduce melanoma by 80% and the other claiming that sunscreen use has been linked to fertility problems in men.

So, what’s a reader to do? Risk skin cancer or give up hopes of easily conceiving a child? The answer: look a little closer and you will find that neither study is particularly compelling.

Mice that were pre-treated with a chemical

The news coverage that discusses the ability of sunscreen to reduce melanoma incidence was based on a study done in mice who had a chemical, 4-hydroxytamoxifen (4OHT) applied to their skin for 26 weeks. Following this, they were exposed to intense UVB light. The ones who received an SPF 30 sunscreen had a reduced incidence of melanoma, according to an Ohio State University news release.

How might this result apply to humans? That’s a good question. As we frequently point out at, studies in mice are not easily generalized to people. In addition, these mice had a chemical applied to their skin daily and were ONLY exposed to UVB light, which is not representative of the effects of the sun (which also emits UVA light). Although the limitation about the type of light used in the study is included in the coverage, it comes at the end of the article, and could easily get lost in the waves created by the splashy headlines.

For example, ran a headline that reads, “Wearing SPF 30 sunscreen has strong ability to prevent deadliest skin cancer, study finds.”

The lead on the same study from TIME reads, “If you aren’t a regular sunscreen user, you may want to think twice and lather up when you go outside this summer; a new study found that applying sunscreen drastically reduces the risk of skin cancer.”

Add “in mice” to both of those statements to achieve some semblance of what actually happened in the studies.

Sunscreen components were applied directly to sperm

The equally incomplete coverage of a different study in CNN claims, “Evidence mounts that sunscreen could weaken sperm.” In this study, according to an Endocrine Society news release, researchers dissolved UV filters found in products such as sunscreen that are approved in the US and Europe. They found that when these dissolved filters were applied directly to sperm, half of them stopped the sperm from functioning properly.

Again, this study design may prove sunscreen should not be applied directly to sperm, but the implications of applying sunscreen to skin and how that would then affect sperm quality is unclear. However, the story quotes a researcher on the project as noting, “These results are of concern and might explain in part why unexplained fertility is so prevalent.” As we have often pointed out, whenever you see the word “might” in a report about health, you may as well substitute “might not.” The rate at which men with infertility use sunscreen is not even a question addressed in this coverage. While the CNN article goes on to discuss the limitations of the study, it does not recover from the overreach of the headline and first few paragraphs.

Don’t get burned by hot seasonal stories

At the end of the day, there are many clear reasons to use sunscreen during the summer months, including reducing the chances of skin cancer and preventing premature aging of the skin. But maintaining your fertility should not be a concern, at least not based on the study covered by CNN. As HealthNewsReview contributor, Harold DeMonaco notes, “The methods used by Dr. Skakkebak in his study are far from the real world application of sunscreens. I suspect that the amounts used in his experiments would likely cause many other effects other than simply sperm functioning. The fact that these agents may alter sperm function is of academic interest but of little use to the average user and I wonder about the newsworthiness of the study at this point. The topic in general however points to the fact that very little in medicine is black or white.  In reality, the domain is mostly gray.”

The takeaway: be wary of topics that too neatly fit with the season and look out for claims that seem hot, but may leave readers burned.

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Comments (3)

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Erik Kreider

April 29, 2016 at 1:53 pm

One can never rely upon just a single study in science – you have to do a comprehensive review of the relevant scientific literature, and do so critically. Most medical literature indicates that sunscreen use does not reduce melanoma risk, but does have a slight protective effect against basal and squamous cell carcinomas. This is not surprising given that the two types of cancer result from significantly different mutagenic processes. Petrochemical sunscreens do indeed have estrogenic effects based on their structural chemistry, and although they are much less effective than the corresponding sex hormones, their relative dose rates are thousands to tens of thousands of times higher than hormonal therapy. That in itself suggests there might be some issues. Two papers that were published by NIH that get very little attention are in regard to hormonal disruption by petrochemical sunscreen active ingredients and another covering bioaccumulation of oxybenzone certainly support the hypothesis that petrochemical sunscreen active ingredients have subacute toxicity issues and may impact reproductive health. You can find these studies by searching for them on google, “NIH hormonal disruptor sunscreen” and “Oxybenzone bioaccumulation” The former is linked here:

    Erik Kreider

    April 29, 2016 at 1:57 pm

    If you want to avoid the risks petrochemical sunscreen pose, you can use mineral sunscreens such as zinc oxide, that provide all the benefits of sunscreen and limit the pharmacological risks of petrochemicals that are readily absorbed through the skin, into tissues and the blood stream.

Andrew DePristo

May 9, 2016 at 7:13 am

The release by the Endocrine society has more relevant information about the effect of UV filters and cannot be so easily dismissed. First, the levels of UV filters found in people after whole-body application of sunscreens is known. And, the researchers found that 45% of the UV filters tested induced calcium ion influxes in the sperm cells even at doses of the chemicals that are BELOW THIS LEVEL. Second, the sperm cells underwent testing in a buffer solution that resembled the conditions in female fallopian tubes. Taken together, this makes a much stronger case for the effect of UV filters on sperm motility and demonstrate that Mr. DeMonaco’s comments are gratuitous and irrelevant to the study. I have to wonder if he even read the press release or the study.